Fuel pumps and the like often contain filtering apparatus for removing minute particles from fuel or other liquid as it is pumped through an apparatus and dispensed. These filters are typically constructed using an outer metallic can and an inner filter element. Usually the outer metallic can and the inner filter element are a single unit and must be replaced entirely when dirty. When these filters are removed for replacement, the liquid contained within the filter, as well as that contained within the apparatus to which the filter is attached, is often spilled. Such spillage is environmentally unsafe as well as wasteful.
Recently it has become a goal to minimize the spillage of fuel and the accompanying environmental hazards of such spillage. U.S. Pat. No. 5,698,093 assigned to the assignee of the present invention represents one example of a device directed at this problem. The '093 patent teaches a technique of utilizing valves which shut off when the filter can is removed in order to trap fluid within the pumping apparatus. As further described in the '093 patent, the inner filter element is removed from the outer can, and the fluid within the outer can may then be disposed of properly and a new filter element installed. The outer can may then be re-attached and is thus reusable for the life of the apparatus.
While the '093 patent makes significant progress toward achieving a solution to the loss of liquid from the dispensing apparatus, there remains the problem of spillage from the outer can. First, when the outer can is removed from the dispensing apparatus, often the inner filter element remains stuck to the dispensing apparatus. This means that all of the fluid trapped in the filter element begins dripping onto the ground, thereby creating an environmental hazard. Additionally, if the entire filtering apparatus is mounted horizontally, then when it is removed from the dispensing apparatus, the fuel within the can will simply spill.
Other prior attempts to solve the foregoing problems have resulted in less than perfect solutions. For example, U.S. Pat. No. 5,098,559 to Mack represents still another attempt at a solution to the foregoing problems. Once again however, drawbacks similar to those described with respect to the '093 patent have prevented widespread commercial use of such an apparatus.
In view of the foregoing, there exists a need in the art for an improved filtering apparatus which includes: (1) a technique for allowing the inner filter to be replaced separately from the outer can; (2) insuring that such filter does not remain stuck to the pumping apparatus when the outer can is removed; and (3) further minimizing spillage and waste when the can is removed from the dispensing apparatus.